ML19305A376

Annual Operating Rept 1978.

ML19305A376
Person / Time
Site:	05000124
Issue date:	02/06/1979
From:	Parkinson T, Stowe B VIRGINIA POLYTECHNIC INSTITUTE & STATE UNIV., BLACKSB
To:
References
NUDOCS 7903130423
Download: ML19305A376 (11)

Text

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ANNUAL REPORT January 1, 1978 - December 31, 1978 VPI & SU Nuclear Reactor License R-62 February 6, 1979 i

Prepared by: b.

Reactor Supervisor Approved: '

Director, Nuclear Reactor Laboratory Department of Mechanical Engineering College of Engineering Virginia Polytechnic Institute and State University 0 Blacksburg, Virginia 24061 o

7903130423

TABLE OF CONTENTS I. Reactor Operations II. Operator Changes III. Tabulation of Unscheduled Scrams IV. Quarterly Scram Time Tests V. Health Physics VI. Control Rod / Fuel Examinations VII. Reactor Operator Requalification VIII. Facility Change IX. Reactor Audits

I. Reactor Operations:

Reactor operating parameters for 1978 were as follcws:

Quarter Jan-Mar Apr-June July-Sept Oct-Dec Kilowatt-hours 27,323 25,518 15,823 21,510 Hours Critical 311.9 300.1 185.7 257.6 41 Ar Released, mci 43,853 40,956 25,396 34,524 Number of Startups 51 61 35 57 Unscheduled Shutdowns 1 1 0 0 Yearly totals Kilowatt hours 90,174 Mci Ar 144,729 Unscheduled Shutdowns 2 Startups 204 Hours Critical 1055.3

, II. Operator Changes:

Mr. John Nelsor, 'Ir. Vincent Perone, and fr. Christopher Holland successfully completed examinations for Reactor Operator Licenses in May, 1978. Mr. H. Gene Knight completed examination for Senior Reactor Operator in May, 1978. Mr. John Helson left the facility in December, 1978 III. Tabulation of Unscheduled Scrams:

Momentary Power Loss 2 Cause of the momentary loss of building power was not determined.

IV. Quarterly Scram Time Tests:

Quarter Ja n-;iar Apr-June July-Sept Oct-Dec Average Safety #1 0.38 sec. 0.48 sec. 0.47 sec. 0.47 sec. 0.45 sec.

Safety #2 0.467 sec. 0.47 sec. 0.49 sec. 0.50 sec. 0.482 sec.

Shiu Safety 0.403 sec. 0.46 sec. 0.44 sec. 0.44 sec. 0.436 sec.

V. Health Physics:

Area surveys and wipe tests were made on a minimum of a quarterly basis. There were no significant changes in observed radiation levels during the year.

The only radioactive waste released to the environment was Ar through the ventilation stack. The total amounts released per quarter are shown on the operations summary.

VI. Control Rod / Fuel Examinations:

The control rods and reactor fuel were inspected during the week of the refueling (March 19-25). There was no evidence of cracking, pitting, or unusual wear or corrosion. Control rod worths, stringer worths, and reactivity input rates were measured on March 22, 1978.

VII. Reactor Operator Requalification:

Deficiencies in the documentation of monthly operator meetings and individual operating time were detected in an NRC operations audit during preparation of this report. A conversational log of all reactor operations, meetings, and maintenance has been initiated as a backup to other documentation procedures.

VIII. Facility Changes:

The fission chamber used as a signal ss e for the startup channel and the uncompensated ion chamber used for Power Range #2 were replaced with detectors installed in the thermal column region of the reactor. The replacement detectors were located where no experiment could " shadow" the neutron flux from the core, and experimental data for the installation was acquired for several months using spare instrument channels prior to the actual exchange.

Saraples of signal data and the procedures used for the exchange are included as attachments.

The exchange was reviewed by the Radiation Safety Committee prior to effecting, and it was determined that the change did meet the acceptance criteria under 10CFR50.59.

The auxiliary shielding around the reactor which consisted of stacked concrete block has been replaced or augmented by fourteen poured concrete blocks. Since these blocks can readily b~e repositioned with the overhead crane, they will allow easier access to the thermal column region and the north and south beam ports.

Two custom built concrete blocks with integral shielding have been added to the top of the reactor. These have reduced the radiation levels around the vertical beam port while operating and also while being accessed during sample insertion and removal operations.

IX. Reactor Audits:

Audits of various aspects of reactor operations were held twice during the year, with one formal report submitted. The report is included as an attachment.

- Proposal to Shift Location of the Power and Startup Range Detectors from the Top of the Reactor Core to the Thermal Column Stringers ,

Background

The VPI6SU Nuclear Reactor was originally licensed to operate at a maxinum power of 10 KW. In 1969, the license was amended to permit operation at a maximum power of 100 KW. In effecting this change, the neutron detectors were not re-located, but were shielded with cadmium to reduce their output by a factor of approximately ten.

Since 1969, the most significant reactor maintenance problem has been repairing the neutron detector cables and fittings that deteriorated due to the high radiation fields in which they are located. The greatest source of radiation exposure to reactor personnel has been received in carrying out this maintenance. Acco rdingl y, studies have been made of the feasibility of relocating the neutron detectors in regions of reduced radiation intensity. In June of 1977, the intermediate range detector was relocated in the bulk shield tank of the reactor, it. accordance with procedures approved by the Radiation Safety Committee, and has operated satisfactorily since that time. In Itarch, 1978, a fission chamber and an un-compensated ion chamber were installed in the stringers in the graphite thermal column to experimentally determine the feasibility of locating permanent detectors in that location.

Proposal It is proposed to replace the source range neutron detector now installed in the core top area (southeast corner) with an identical fission chamber installed in the graphite thermal column four inch removable stringer located at the

.nidplane of the reactor core vertically, and to replace the Power range One uncompensated ion chamber with an identical detector located si'milarly to the fission chamber. (See attached drawings.) The Source range detector change procedure is greatly simplified by virtue of five months of operation with an identical indicating circuitry to that currently used as the. reactor source range instrument. The chamber current for the power range instrument has been observed and logged for five months, facilitating recalibration of the power range instrument to accomodate the detector substitution.

Discussion The results of five months of study indicate a much greater correlation between the power indications from the thermal column detectors and the calorimetric reactor power than has been observed with the core top detectors. Additionally, the detector stability over long operating time is greater. The signal-to-noise ratio of the fission chamber is significantly greater than with the core top detector, and the signal level is approximately 40 times that of the core top detector. Approximately 1.5 decades of overlap is provided between the Intermediate Range indication f rom the Shield tank detector and the Thermal column Source range detector.

Several advantages become apparent in this relocation. The position of the detectors is such that they will not be disturbed during annual in-core maintenance, and the absence of cadmium shielding will mean less signal level change if detector maintenance is required. The moisture-free environment means stable operation

. can be provided without requiring sealed environmental chambers for the detectors and connectors.

. Safety Analysis One possible safety question was considered - does the new location allow an experiment to shadow the detector.

There is no space between the reactor core graphite and the thermal column graphite other than that occupied by a two inch lead gamma curtain. Therefore, it is not possible for an experiment to shadow the detector unless the experiment is installed in the same stringer hole as the detector. This will be forbidden.

Acceptance Criteria The acceptance criteria shall be that the detectors installed in the graphite thermal column be identical to the the detectors currently in use, and that the performance of the detectors in the new locations provide signal levels greater than or equal to those currently provided, with equal or better stability.

The data accumulas ed over the five month observation period indicates that these criteria are met.

Installation Procedure The installation of the thermal column detectors as operating instrumentation shall be effected by:

1) Installation of conduit or other such suitable shielding to protect the signal cables to the thermal column.

2) Evaluation of the accumulated data to assure acceptance criteria have been met by all licensed Senior Reactor Operators at this facility and by one consulting member of the Radiation Safety Committee.

3) Calibration of the Power Range One instrument to provide 100% indication at the current level observed from the thermal colunn UCIC at 100%

calorimetric power.

4) Connection of the thermal column detectors and performance of a reactor flux calibration at a reactor power of 10%.

5) A minimum of 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> operation at power levels less than 90% with no observable deviation from normal indications on the replaced detector instrumentation.

The proposed change may be effected prior to approval by the Reactor Licensing Branch of the U.S. Nuclear Regulatory Commission in accordance with 10 CFR 50.59 if, in the judgment of the Radiation Safety Committee, the change does not: 1) increase the probability of an accident or malfunction of equipment important to safety previously evaluated in the Safety Analysis Report, or; 2) create the pos-sibility of an accident or malfunction of a dif ferent type than any evaluated previously in the Safety Analysis Report, or; 3) reduce the nargin of safety as defined in the basis for any Technical Specifications.

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/ -(~ g Procedure for Reactor Shielding Replacement and Subsequent Reactor Festart s

1. Perform a neutron and gamma survey (with the reactor at 100 KW) of the stacked block to be replaced by the new shield blocks.

Record the readings on a detailed survey map.

2. Shutdown the reactor, remove the loose blocks and install the new shield blocks.

3. Startup the reactor and level power of f at 10KW. Perform a neutron and gamma survey to insure no unsatisfactory radiation levels exist.

4. Increase reactor power to 100 KW and again perform a neutron and gamma survey at the same points surveyed in step # 1.

5. Compare the two survey maps. If the final levels are greater than the initial radiation levels, shutdown the reactor and correct the shielding configuration to reduce the radiation levels. If the final levels are less than or equal to the initial 1cvels, continue normal reactor operations, Jtetain both survey maps as a permanent record.

This procedure meets the requirements of VI. 6. III, Procedure on Reactot Pxocedures. j 73 7 ,d m ,. -

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t Safety Analysis of Reactor Shielding Replacement The only hazard associated with reactor shielding replacement would '

be thehigher shieldsthan normally acceptabic radiation Icvels in the vicinity of replaced. This hazard will be alleviated by three methods:

1. The reactor will not be operated while replacing the shields.

2. The new shield blocks are wider than the existing loose stacked block, thus providing for lower radiation levels around the perimeter of the reactor.

3. A survey according to procedure will be performed to detect any abnormal radiation levels.

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• ...* fa 1 ' 1978 In Reply Refer To:

RII:JHD 5'-124/78-1 Virginia Polytechnic Institute and State University Atta: Dr. T. F. Parkinson, Director Nuclear Laboratory Blackaburg, Virginia 24060 Gentlemen:

This reftra to the inspection conducted by Mr J. H. Davis of this .

office on January 16-20, 1978, of activities authorized by NRC Licence "o. R-62 for the Virginia Polytechnic Institute facility, and to the discussion of our fin 31ngs held with Mr. f. F. Parkinson at the coa-clusien of the inspection.

Areas exanined during the incpection and our findings are discussed in the encloccd in9pection report. Within these areas, the inspection consit:ted of selective examinations of procedures and representative records, interviews with personnel, and observations by the innpector.

Within the scope of this inspection, no items of noncompliance were d i sclosed .

i In accordance with Section 2.790 of the NRC's "Fales of Practice",  ;

Part 2, Title 10, Code of Federal Regulations, a copy of this letter j and the enclosed inspection report will be placed in the NRC's Public Document Rocc. If this report contains any information that you (or your contractor) believe to be proprietary, it is necessary that you n u e a written application within 20 days to this office to withhol<!

such information fron public disclosure. Any such applicatica nust include a full statement of the reasons on the basis of which it is claimed that the information is proprietary, and should be prepared so that proprietary information identified in the application is contained in a scparata part of the document. If ve do not hear f rc :.2 you in this regard within the specified perled, the report will be placed in tite Public Document Room.

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, LC Virginia Polytechnic Institute s should you have any questions concerning this Ictter, we will be glad to discuac thc= with you.

Sincerely, sj, )A h RbK J. T. Sutherland, Chief Fuel Facility and Materials Safety Branch

Enclosure:

Inspcction Report No. 50-124/78-1 e

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